This invention relates to photography in general and, more particularly, to dyes which are useful in providing diffusion transfer color images and to photographic products and processes employing such dyes.
Multicolor images formed in accordance with the principles of subtractive color photography employ yellow, magenta and cyan image dyes. The yellow dye ideally transmits only green and red light and absorbs only blue light, and thus is sometimes referred to as "minus blue". In like manner, the magenta ("minus green") dye ideally absorbs only green light and transmits only blue and red light, and the cyan ("minus red") dye ideally absorbs only red light and transmits only blue and green light. Unfortunately, the dyes available for use in subtractive color photography are not "ideal" dyes, but tend to absorb some of the light that they ideally should transmit. This extra absorption results in less effective reproduction by the final image of one or more colors present in the original subject.
This problem may be illustrated by considering the reproduction of blue light: a multicolor photosensitive element, containing a blue-sensitive silver halide layer, a green-sensitive silver halide layer and a red-sensitive silver halide layer, said silver halide layers having associated therewith, respectively, a yellow image dye-providing material, a magenta image dye-providing material, and a cyan image dye-providing material, is exposed to blue light in an amount effective to fully expose the blue-sensitive layer. Only the blue-sensitive silver halide layer is exposed; the green-sensitive and red-sensitive silver halide emulsion layers remain unexposed. If such an exposed photosensitive element were processed by diffusion transfer techniques, the yellow image dye-providing material would remain in the developed photo-sensitive element (negative component) but magenta and cyan image dyes would be transferred to the image-receiving layer (positive component). Since the magenta and cyan image dyes are "minus green" and "minus red" respectively, the combination and magenta and cyan dyes appear blue, i.e., they transmit blue light to the viewer and absorb green and red, thus reproducing the blue record of the original object.
In the art of photography there is a continuing search for new image-forming dyes. The present application is drawn to novel image dye-providing materials which are useful in photography.